Pitching takes practice for sure so encourage your players to go in backyard on non-game days. Another issue with beginner pitchers is they all want to try - but encourage them to 'try' not during game but during a practice. The goal is for players who can get it over plate 50%+ of the time get to pitch in games.
Some helpful tips:
Setup - two feet on or in contact with the mound. Hands together. Full stop.
Step – full stride with (left) leg. Push off mound with right leg. Use legs (not arms) for power.
Release Point - release the ball at the(right) leg. Follow all the way through!
Drills - wrist flips. Half windmills. Full elbow extension drills.
We suggest that beginner pitchers pitch from the 'T'- not windmill
Other Video Resources: